首页
登录
职称英语
The gravitational pull of the earth and moon is important to us as we attemp
The gravitational pull of the earth and moon is important to us as we attemp
游客
2024-05-09
1
管理
问题
The gravitational pull of the earth and moon is important to us as we attempt to conquer more and more of outer space. Here’s why.
As a rocket leaves the earth, the pull of the earth on it becomes less and less as the rocket roars out into space. If you imagine a line between the earth and the moon, there’s a point somewhere along that line, nearer to the moon than to the earth, at which the gravitational pull of both the earth and the moon on an object is just about equal. An object placed on the moon side of that point would be drawn to the moon. An object placed on the earth side of that point would be drawn to the earth. Therefore, a rocket need be sent only to this "point of no return" in order to get it to the moon. The moon’s gravity will pull it the rest of the way.
The return trip of the rocket to the earth is, in some ways, less of a problem. The earth’s gravitational field reaches far closer to the moon than does the moon’s to earth. Thus, it will be necessary to fire an earthbound rocket only a few thousand miles away from the moon to reach a point where the rocket will drift to earth under the earth’s gravitational pull.
The problem of rocket travel is not so much concerned with getting the rocket into space as it is with guiding the rocket after it leaves the earth’s surface. Remember that the moon is constantly circling the earth. A rocket fired at the moon and continuing in the direction in which it was fired would miss the moon by a wide: margin and. perhaps continue to drift out into space until "captured" in another planet’s gravitational field. To reach the moon, a rocket must be tired toward the point where the moon will be when the rocket has traveled the: required distance. This requires precise calculations of the speed and direction of the rocket and of the speed and direction of the moon.
For a rocket to arrive at a point where the moon’s gravity will pull it the rest of the way, it must reach a speed called the velocity of escape. This speed is about 25, 000 m/les (about 40,200 kilometers) per hour. At a speed less than this, a rocket will merely circle the earth in an orbit and eventually fall back to the earth. [br] What does "an earthbound rocket" in Sentence 3 Para. 3 mean?
选项
A、A rocket sent from the earth to the moon.
B、A rocket sent from the moon to the earth.
C、A rocket made of earth.
D、A rocket with no purpose.
答案
B
解析
词汇理解题。本题也是对课文意思的间接考查,根据该句后面的阐述,我们知道这种火箭飞船是由月球向地球发射的,这样只要发射几千英里就可到达地、月之间的平衡点了。
转载请注明原文地址:https://tihaiku.com/zcyy/3590114.html
相关试题推荐
[originaltext]W:Ican’tbelieveKarenislateforsuchanimportantoccasiona
[originaltext]W:Ican’tbelieveKarenislateforsuchanimportantoccasiona
[originaltext]W:Ican’tbelieveKarenislateforsuchanimportantoccasiona
[originaltext]W:Ican’tbelieveKarenislateforsuchanimportantoccasiona
Iwouldratheryou______(随身携带那些重要文件).took/carriedthoseimportantdocumentswith
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
随机试题
下列不属于企业投资港口、航道工程建设项目建设程序的是( )。A.根据核准的项目
事关全面建设小康社会大局,必须始终作为全党工作重中之重的是解决好( )A.“
关于IgG的叙述,下列哪项是错误的A.是一种球蛋白 B.能通过胎盘 C.血清
青霉素G水溶液不稳定,久置可引起的变化是()A.药效下降并诱发过敏反应
项目的实施期指的是()。A、自项目开始到项目完成 B、自决策到动用前准备
2011年上半年,我国软件产业实现软件业务收入8065亿元,同比增长29.3%,
A.簇晶B.方晶C.针晶D.沙晶E.柱晶药材牡丹皮的粉末中有
根据以下资料 21世纪头10年,金砖国家整体经济平均增长率超过8%,远高于发达
2020年1-12月份,全市固定资产投资3815.36亿元,同比增长6.1%。房
个人质押贷款还款方式不包括( )。A.等额本息还款法 B.差额等息还款法
最新回复
(
0
)